gev-tev emission from inverse-compton scattering processes in grbs
DESCRIPTION
GeV-TeV emission from inverse-Compton scattering processes in GRBs. Xiang-Yu Wang. Penn State University Collaborators: P. Meszaros, Z.Li, Z. G. Dai & T. Lu. GRB-shock acceleration. Protons- Electrons- Shock acceleration: ~10 TeV. - PowerPoint PPT PresentationTRANSCRIPT
GeV-TeV emission from inverse-Compton scattering processes in GRBs
Xiang-Yu Wang
Penn State University
Collaborators: P. Meszaros, Z.Li, Z. G. Dai & T. Lu
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
shock acceleration : (e.g. Waxman 1995; Vietri 1995)
photo-meson process: (e.g. Waxman & Bahcall 1997; Bottcher & Dermer 1998)
proton synchrotron radiation (e.g. Vietri 1997; Totani 1998)
GRB-shock acceleration
Protons-
Electrons- Shock acceleration: ~10 TeV
pp 0 0
eV10~ 20
7, 10~ Maxeacccool tt
5, 10 MaxeX-ray afterglows
e.g. Li & Waxman 2006
Leptonic inverse Compton scattering
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
Inverse-Compton scattering in GRB shocks
Internal shock IC: e.g. Pilla & Loeb 1998; Razzaque et al. 2004
External shock IC reverse shock IC: e.g. Meszaros , et al. 94; Wang et al. 01; Granot & Guetta 03
forward shock IC: e.g.Meszaros & Rees 94; Dermer et al. 00; Zhang & Meszaros 01
Credit P. Meszaros
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
I will include…
1. VHE photons from GRB early external shocks--very early afterglow phase
2. VHE photons related to X-ray flares: X-ray flares photons are IC scattered by electrons in afterglow shocks
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
1. IC emission from very early external shocks
Shocked shell
Shocked ISM
Cold ISM
Coldshell
pressure
FSRS
CD
1) (rr)2) (ff)3) (fr)4) (rf)
Four IC processes
(Wang, Dai & Lu 2001 ApJ,556, 1010)
At deceleration radius, T_obs~10-100 sForward shock---Reverse shock structure is developed
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
Energy spectra---
1
0
max
min
'3 xfxdxgNdrf TIC
;1,5.2,01.0,6.0,10E a) 53 nperg Be
f
At sub-GeV to GeV energies, the SSC of reverse shock is dominant; at higher energies, the Combined IC or SSC of forward shock becomes increasingly dominated
See also Wang, Dai & Lu 2001, ApJ,546, L33
Reverse shock SSC (r,f) IC
(f,r) ICForward shock SSC
Log(E/keV)
GLAST 5 photons sensitivity
(Wang, Dai & Lu 2001 ApJ,556, 1010)
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
One interesting GeV burst
−18 s – 14 s
14 s – 47 s
47 s – 80 s
80 s – 113 s
113 s – 211 s
Gonzalez et al. 03: Hadronic model
Leptonic IC model:
Granot & Guetta 03 Pe’er & Waxman 04 Wang X Y et al. 05, A&A, 439,957
GRB941017
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
2. VHE photons from x-ray flare-blast wave interaction
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
~30%-50% early afterglow have x-ray flares, Swift discovery
Most striking flare GRB050502B discovered by Swift
Flare light curves: rapid rise and decay
<<1 Afterglow decay consistent with
a single power-law before and after the flare
X-ray flares: late-time central engine activity
Burrows et al. 2005Falcone et al. 2006
amplitude: ~500 times above the underlying afterglow
GRB050502B
X-ray flares occur inside the decelerationradius of the afterglow shock
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
IC between X-ray flare photons and afterglow electrons (Wang, Li & Meszaros 2006)
Cnetral engine
X-ray flare photons
Forward shock region
Cartoon
X-ray flare photons illuminate the afterglow shock electrons from inside
also see Fan & Piran 2006: unseen UV photons
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
Flare photons is the dominant cooling source of afterglow electrons Flare photons is the dominant cooling
source for electrons in the afterglow jet
>
Flare photons make the afterglow electrons fast-cooling
O’Brien et al. 2006
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
IC GeV flare fluence-An estimate So most energy of the newly shock electrons will be lost into IC emi
ssion
X-ray flare peak energy
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
Klein-Nishina suppression is unimportant below TeV
Klein-Nishina cutoff
But at high redshift, the infrared background absorption will be important
Magic, Milagro, HESS, etc.
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
Anisotropic IC scattering effect Effect: decrease the power along the seed photon bea
m direction, but increase larger angle emission, about a half within (Wang, Li & Meszaros 2006)
If , when integrated over angles, the received IC fluence will not be reduced.
Suppose the sphere geometry: every direction has the same fluence.
e.g. Ghisellini 1978; Brunetti 2000; Fan & Piran 2006
The IC fluence will not change
/2
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
Temporal behavior of the IC emission Not correlated with the X-ray flare light curves. IC emission will be
lengthened by the afterglow shock angular spreading time and the anisotropic IC effect
XRFobs tRRR
t 222
~2
2
2
Time delay relative to the flare time
/2 to/1 from cone in the emitted photons IC
GLAST might be able to distinguish them
/2
Self-IC of flaresWang, Li & Meszaros 2006 also see Galli et al. poster
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
Delayed GeV emission ---GRB940217
EGRET on board Compton
Hurley et al.1994Was there a delayed X-ray flare ?
See also Zhang & Meszaros 2001 Wei & Fan 2007
"The First GLAST Symposium", Feb.5-8 2007, Stanford University
Summary
IC in early external shocks
IC of x-ray flares
What could GLAST tell us? Origin of GeV photons (both prompt and delayed): Spectral and temporal pro
perties
Maximum energy of the shock accelerated electrons :
Magnetic field in the shocks: …
BphsynIC UULL //
?, Maxe
Both are promising VHE photon sources for GLAST